How to Electronically Sign a PDF on iPhone | Built-In Markup Method

You can sign a PDF on an iPhone using the Markup tool inside the Files app with a finger-drawn signature saved for reuse, and no third-party software is needed on devices running iOS 17 or later.

Signing a PDF from an iPhone should be a quick task, not a research project. Apple added a native signature tool to iOS 17, and it handles most everyday PDFs without any extra apps. Whether a contract arrived in email or a rental agreement is saved to your phone, the process takes about twenty seconds once you know where to look. This walkthrough covers the built-in route, the free Adobe option, and when you need something heavier.

What You Need Before You Start

The built-in signature feature requires iOS 17 or later. Apple released iOS 17 on September 18, 2023, and it runs on iPhone 8 and newer models, including the iPhone SE (2nd and 3rd generation) and the iPhone 16 series. No carrier plan or Apple subscription is required — it is a free native feature available globally wherever iOS 17 is supported.

How to Sign a PDF Using the Files App

The Files app is the primary method for signing saved PDFs on an iPhone running iOS 17. Follow these steps exactly to create and place your signature. The signature is drawn with your finger, not typed as text.

1. Open the Files app and tap the PDF to open it.
2. Tap the Markup icon — a pen tip inside a circle, located in the top-right corner.
3. Tap the + (Plus) icon in the markup toolbar at the bottom of the screen.
4. Select Add Signature (the option reads Signature if one is already saved).
5. To create a new signature, tap Add (+) , sign your name on the canvas using your finger, and tap Done.
6. Drag the signature image to the correct spot on the document. Pinch or drag the corner dots to resize it.
7. Tap Done in the top-left corner to save the signed PDF.

A the signature appears on the page exactly where you placed it. If you need to sign a second document later, your saved signature is available immediately in the same Signature menu.

How to Sign a PDF Attached in Mail

PDFs that arrive as email attachments can be signed directly without first saving them to Files. The Mail app includes the same Markup tools.

1. Open the email and tap the PDF attachment to preview it.
2. Tap the Markup icon — it resembles a toolbox in the top-right corner of the preview.
3. Tap the + icon, choose Signature, then select a saved signature or create a new one.
4. Position and resize the signature, then tap Done twice. The signed PDF is attached to a reply.

How to Sign a PDF Using the Notes App

The Notes app provides an alternative route when the PDF is a scanned document you just captured. This method works well for paper forms photographed in the moment.

1. Open Notes and create a new note or select an existing one.
2. Tap the camera button above the keyboard, then choose Scan Documents or Choose Photo.
3. After the scan appears, tap the document thumbnail, then tap the Markup icon (pen tip in a circle).
4. Tap + and select Add Signature to place your signature on the scanned page.
5. Tap Done to save the signed scan back into the note.

A the scanned document displays your signature overlaid on the page. The signed image can then be shared or exported from the note.

How to Sign a PDF With Adobe Acrobat Reader

For iPhones still running iOS 16 or older, the free Adobe Acrobat Reader app is the best alternative. The signing tool is free with no mandatory in-app purchases.

1. Download Adobe Acrobat Reader from the App Store.
2. Open the PDF in the app and tap the pencil icon at the bottom of the screen.
3. Select Fill & Sign from the menu. Do not select Edit — the signature tool is inside Fill & Sign.
4. Tap the Signature icon at the bottom (a pen nib) and then tap Create Signature.
5. Draw your signature with a finger, Apple Pencil, or a compatible stylus. Tap Done to save it.
6. Tap the saved signature to place it on the document, then drag it into position.

A the signature appears as a graphic in the document. Adobe also saves it for future use across other PDFs in the app.

Common Mistakes and Important Caveats

Mistake: Trying This on iOS 16 or Earlier

The native Markup signature feature debuted in iOS 17. If the iPhone runs iOS 16 or older, the + icon inside Markup will not show a Signature option. On those devices, use Adobe Acrobat Reader or another third-party app for signing.

Mistake: Selecting Edit Instead of Fill & Sign in Adobe

Adobe’s Edit mode lets you modify text and images, but the signature tool lives exclusively under Fill & Sign. Tapping the pencil icon and checking the menu before starting saves a round of backtracking.

Mistake: Typing a Name Instead of Drawing a Signature

The native Markup tool also has a text box option. Tapping that creates typed text, not a signature graphic. For a legally recognizable handwritten signature, select Add Signature from the + menu and draw it by hand.

What the Native Signature Actually Is

The signature created in Markup is a graphic image of handwriting, not a cryptographic digital ID (like a PKI certificate). For routine contracts, rental agreements, and permission slips, that is sufficient. For documents that require cryptographic verification — such as certain real estate closings or government filings — use DocuSign or Adobe Acrobat Pro, which provide enhanced security layers and audit trails.

Locked or DRM-Protected PDFs

The native tool cannot modify PDFs that are locked or have digital rights management (DRM) that prevents editing. Those files display a padlock icon and must be opened in a compatible third-party viewer that supports signing the locked document.

When to Use a Third-Party Signing App

The native Markup signature handles most one-person signing tasks without any extra cost. Third-party apps add value in three specific scenarios. If the document requires signatures from multiple people, DocuSign or HelloSign manage the workflow from a single link. If cryptographic authentication is mandated by the document’s recipient, DocuSign and Adobe Acrobat Pro provide verifiable digital IDs. If the iPhone runs iOS 16 or older, Adobe Acrobat Reader offers the same free signing capability that iOS 17 built into the system.

A quick check: if the document has no padlock icon and you are the only signer, the Files app method will finish the job without downloading anything. If any of the three limitations above apply, pick the corresponding app from the table and move on.